Actually, the rules were clear: if you install the app and do the backup of the wallet, you're eligible to get the airdrop. There was no mention of having the app installed on the phone at the time of the snapshot. However, if you don't uninstall the app (and I'm wondering how do they know if you uninstalled the app), but only cleared the cache and create new wallets and do the backup procedure, you should be able to get more airdrops using only one phone.
I remember I read something on the VIO official chat (or was it Eidoo?) where someone was asking this question and they agreed that it was like this.
If now the requirement is to be "active" (and what does it mean?) it is a change in the rules.